Corrosion resistant sulfurized-phosphorized extreme pressure lubricant



nited States ate t CORROSION RESISTANT SULFURIZED-PHOS- PHORIZED EXTREMEPRESSURE LUBRICANT Allan A. Manteufiel, Crystal Lake, George W. Ayers,Chicago, and William D. Gilson, Crystal Lake, 11L, assignors to The PureOil Company, Chicago, 111., a corporation of Ohio Application September13, 1956 Serial No. 609,543

7 Claims. (Cl. 252-44) No Drawing.

ing compositions as E.P. lubricant additives is Wellknown):

Each type of additive has-its advantagesand;dis'advair tages. Thehalogen-containing additives, while: capable of imparting highload-carrying characteristics. to oils, have the disadvantage of beingcorrosive and hydrolyzing in service to formobjectionable acids. Theability of sulfur to impart high load-carrying characteristics to alubricating oil is dependent on the activity of the sulfur, which inturn is dependent on the tightness with which it is chemically bound ina compound. Elemental or loosely bound sulfur, while imparting highload-carrying characteristics, is too corrosive to be allowed to remainin an automotive differential or other gear assembly over a long periodof time. The same is true of the phosphorus sulfides. On the other hand,sulfur and phosphorus sulfides when tightly bound chemically to organiccompounds such as fatty acids, fatty esters, fatty alcohols andterpenes, impart excellent load-carrying characteristics to alubricating oil and are substantially non-corrosive. However, additivesof this type will not give the desired protection against wear to newgears during the initial break-in period.

An object of this invention-his to'provide artextreme' pressurelubricant. Anotherobject of this invention is to provide a compositionwhich can be added to mineral and other lubricating oils to impartthereto extreme press'ure characteristics. A further object of theinvention is to provide a lubricant which will protect gears againstwear during the initial break-in period and during the subsequentrunning life of the gears. Still another object of the invention is toprovide a composition which can be added to mineral oil and other typesof lubricants to enable such lubricants to satisfactorily lubricateautomotive gears during the initial break-in period and during thesubsequent running life thereof. A still further object of the inventionis to provide an extreme pressure lubricant which will satisfactorilylubricate gear assemblies during the initial break-in period and duringthe subsequent running life thereof without causing undue corrosion ofthe gear elements. Still another object is to provide a method formaking the aforesaid compositions and lubricants.

Other objects of the invention will become manifest from the followingdetailed description of the invention.

In co-pending application Serial No. 606,585 there is disclosed alubricating oil composed of a major portion of mineral lubricating oil,sulfurized and phosphorized fatty material and free sulfur orsulfur-liberating compound, with or without materials which willaccelerate the chemical fixation of the free sulfur, namely, naphthenatesalts and ammonium or amine salts of sulfonic acids. We have discoveredthat the conversion of the active sulfur to a non-corrosive form can beaccelerated by incorporating in the oil a small amount of an organicphosphite or trithiophosphite (also called a phosphorotrithioitc). Theaccelerators used in accordance with our invention may be represented bythe general formula (RS) P (phosphorotrithioites) and (RO) P(phosphites) in which the R may be an alkyl, aryl or alkylaryl radical.As specific examples of compounds falling within the scope of thisinvention may be mentioned triethyl phosphorotrithioite, diethylhydrogen phosphite, and tricresyl phosphite. Any alkyl, aryl oralkylaryl phosphite or phosphorotrithioite may be used which issutficiently 'soluble in the finished oil so that it does notprecipitate out during storage.

The phosphites and phosphorotrithioites are effective for renderingsulfur non-corrosive, either in the presence or absence of naphthenatesalts. In order to improve the anti-weld properties of lubricants inaccordance with our invention, we preferrto. incorporate into thelubricant Glenda; naphthenatecsaltisnclnas lead naphthenate. The

sulfurized-phosphorized fatty material, sulfur: and lead naphthenatecooperate to provide the required anti-weld properties to the lubricantduring the break-in period and the sulfurized-phosphorized fattymaterial in conjunction with dibenzyl'disulfide imparts the requiredload-carrying properties to the oil during operation subsequent to thebreak-in period.

As sulfurized and phosphorized compositions which are effective for thepurpose of our invention we prefer sulfurized and phosphorized fattybodies such as those made in accordance with Whittier et al., Patent2,211,306. As therein disclosed, such sulfurized and phosphorized fattybodies are prepared by sulfurizing a fatty material such as vegetable,animal, or marine oils and waxes, including but not limited to woolgrease, cotton seed, castor, rape seed, sperm and lard oils, andsynthetic esters of high molecular weight, mono-unsaturated fatty acids(C C such as glyceryl trioleate, propylene glycol dioleate and butyleneglycol dioleate, at a temperature of approximately 330-340 F. withelemental sulfur until a satisfactory'copperstrip test is obtained, andthen phosphorizing' the sulfurized material with a phosphorus sulfide,preferably phosphorus sesquisulfide,

at a temperature of about 220-230" Fluntil'a satisfactorycopper strip isobtained.

Instead of following the process set forth in the aforesaid Whittier etal. patent, the initial sulfurization step may be terminated prior tothe time a satisfactory copper strip test is obtained, that is, when thecopper strip shows a tan color, and then phosphorized with a phosphorussulfide for a sufficiently long period of time to more firmly bind thesu'fur and phosphorus. This method is particularly effective wherehigher amounts of phosphorus sescguisulfide within the limits of thosedisclosed in the aforesaid patent are used in the phosphorization step.As a specinc example, lard oil was mixed with 7.5% of sulfur and thenwas stirred with constant agitation in a kettle at a temperature of325-340 F. Heating was continued for approximately four hours, at whichtime the copper strip gave a tan color upon immersion in a sample of theproduct at 300 F. for one minute. The mixture was then rapidly cooled toapproximately 220 F., 0.8% by weight of phosphorus sesquisulfide wasslowly added in finely divided form, and the reaction was allowed tocontinue at 220-230" F. for a period of eight hours, after which themixture was rapidly cooled to F. and thereafter allowed to cool to roomtemperature. The final product contained 7.85% sulfur and 0.45% phos- 3phorus by weight and gave a tan color on the strip test at 220 F. forone minute.

In preparing sulfurized-phosphorized fatty materials in accordance withthe method just described, the fatty material may be reacted with about5 to of sulfur in the first stage and with from about 0.4 to 5% ofphosphorus sesquisulfide or equivalent amount of other phosphorussulfide in the second stage. This method of preparingsulfurized-phosphorized fatty materials, in which sulfur is not tightlybound in the first stage and relatively large amounts of phosphorussulfide are reacted in the second stage, is disclosed and claimed inco-pending application of P. R. Chapman and A. Manteuffel, Serial No.553,419.

Instead of using elemental sulfur in conjunction with thesulfurized-phosphorized fatty material, we may add to the oil anunstable sulfur compound which will release elemental sulfur as, forexample, dibenzyl trisulfide or other alkyl, aryl or arylalkylpoly'sulfides containing three or more sulfur atoms in the molecule. Aphosphorus sulfide such asphosphorus sesquisulfide suspended ordissolved in the mineral oil will also function to provide the anti-weldproperties for which the elemental sulfur is added. If desired, bothsulfur and a phosphorus sulfide such as phosphorus sesquisulfide may beused in combination within the limits of the amounts specified above forsulfur. If a sulfur-liberating compound is used, it should be added inamounts sufficient to liberate the desired amount of sulfur.

In preparing gear oils in accordance with our invention, the sulfur oractive sulfur-containing compound is dissolved in a portion or all ofthe mineral oil at a temperature of about 270290 F. After the additionof the sulfur or active-sulfur compound is complete, the temperature ofthe oil is reduced to about 200 F. before adding thesulfurized-phosphorized fatty material. It is important to reduce thetemperature to this level to avoid immediate or rapid reaction,inactivation, or absorption of the sulfur into a substantially lessactive form. A suitable temperature for admixture of thesulfur-containing oil and the sulfurized-phosphorized fatty body isabout l60200 F.

The manner of mixing the several constituents together or the order inwhich they are admixed is not important, provided temperatures areproperly adjusted to a level which will permit solution of the additivesin the oil within a reasonable period of time without causingsubstantial reaction between the active sulfur and the sulfurizedcopperfur compound to sulfurized-phosphorized fatty material is too high, thesulfur will not be completely absorbed and the corrosive condition ofthe gear oil will continue for an indefinite period of time withresultant harmful wear of the gear parts. The amount of sulfur which canbe chemically absorbed is determined by the amount of thesulfurized-phosphorized fatty material and phosphite orphosphorotrithioite present and also by the amount of sulfur bound inthe sulfurized-phosphorized material. A sulfurized-phosphorized materialcontaining a relatively low amount of bound sulfur, as, for example, 5%by weight, enables the use of a larger amount of free sulfur or activesulfur-containing material than does a sulfurized-phosphorized materialcontaining a higher amount as, for example, 10% of bound sulfur. Ingeneral, we have found that an amount of sulfur or equivaent activesulfur-containing compound between 1 and 50% of the ,quantity ofsulfurized-phosphorized fatty material is cfphosphorized fatty material.The sulfurized-phosphorized fatty material, dibenzyl disulfide,naphthenate salt and phosphite or phosphorotrithioite, as well as otheradditives such as pour point depressors, V.I. improvers and antifoamagents, may be added separately to the oil or may be admixed togetherand added as an admixture. They may be dissolved directly in the oil inwhich the sulfur or active-sulfur compound which has been previouslydissolved, or they may be admixed with a portion of the oil to which thesulfur or active-sulfur compound has not been added and this portionadded to the portion containing the sulfur or active-sulfur compound. Weprefer to add dibenzyl disulfide or equivalent disulfide as disclosed inclaims in Reissue Patent 22,911, in order to improve the load-carryingproperties of the oil. We also, preferably, incorporate in the finishedlubricant a sufficient amount of aromatic extract obtained in thesolvent extraction of mineral lubricating oil fractions by means ofphenol, furfural, nitrobenzene and equivalent solvents in order toprevent precipitation.

In order to realize the benefits of our invention, it is necessary toadjust the proportions of sulfurized-phosphorized fatty material andsulfur, or activesulfur compound, so that the active sulfur is absorbedor chemically bound by the sulfurized-phosphorized material and does notremain in the oil in a corrosive form over a long period of time. If theratio of sulfur or active-sulfective in providing initial anti-weldcharacteristics to the oil during the break-in period and of beingsubsequently absorbed or reacted with the sulfurized-phosphorized fattymaterial to a substantially non-corrosive state. We prefer an amount ofsulfur equivalent to about 3 to 10% by weight of thesulfurized-phosphorized fatty material.

The amount of free sulfur or active sulfur-containing material to beadded will be determined to some extent by the nature of the gears to belubricated. For example. in the case of phosphate-coated gears thenumber of miles required for breaking them in is probably not more thanand may be as low as 25 to 50. In such cases, therefore, it may bedesirable to incorporate smaller amounts of sulfur so that the sulfurwill be bound in an inactive or non-corrosive form within a short periodof time, probably not more than 24 hours. On the other hand, greengears," that is, gears which are not precoated, are usually consideredto be broken in after 500 miles of recommended driving speed. In suchcases, sufficient sulfur should be present so that it will not becompletely bound before the end of the period required to drive 500miles, which on an average may be approximately one week.

The amount of sulfur required in the oil to furnish anti-weld protectionduring the necessary period of breakin can be approximated by subjectingan oil blend maintained at approximately 200' F. for the requisiteperiod of time to the copper strip test. performed by immersing a cleancopper strip for three minutes in a sample of the oil maintained at atemperature of 210 F. The appearance of the strip after this testprovides an indication of the amount of corrosion which occurred andhence the extent to which the active sulfur has been bound in anon-active form. If the color of the strip remains clear and bright itis indicative of the fact that the sulfur has been tightly boundchemically and is in non-corrosive form. As the color of the stripprogresses through light orange, orange. light brown, medium brown,mottled brown and brown-black, it indicates that the oil is more andmore corrosive.

In order to demonstrate the effectiveness of compositions made inaccordance with our invention, a number of blends were prepared andsubjected to the copper strip corrosion test. The blends tested and thecorrosion tests on each blend are given in the following table. Blendswere made by dissolving free sulfur in approximately half of the totalmineral oil, previously blended, at a temperature of 270-290 F. withstirring. The total mineral oil consisted of a blend of mineral oil,bright stock and solvent extract. These three constitutents were blendedtogether to give the desired finished viscosity and V.I. The extract oilwas used to insure complete compatibility of the additives, particularlysulfurized-phosphorized lard oil, in the finished oil andto inhibitprecipitation.

After the sulfur had been dissolved in a portion of the mineral oil, theremainder of the oil was added, resulting in cooling of the'solution'tobelow 200 F. sulfurizedphosphorized la'rd oil, dibenzyl disulfide','leadnaphthenate and phosphite or phosphorotrithioite were then added asindicated in the specific blends. During the addition of theseadditives, the oil was at a temperature between 160 F. and 200 F. Thetemperature was maintained below 200 F. to avoid premature inactivationof the sulfur.

Portions of the blends were heated in an oil bath to 200 F. and sampleswere subjected to the three-minute copper strip test at 210 F. afterreaching bath temperature and thereafter at intervals of one hour, twohours, twenty-four hours, and one Week. The temperature of 200 F. wasselected as representing the average temperature to which gear oils aresubjected in service. The sulfurized and phosphorized lard oil used inthe blends given in the ensuing table was made by heating 91.7 parts byweight of lard oil to 285, plus or minus F., and then dusting in slowly,with agitation, 7.5 parts by weight of sulfur. After the addition of thesulfur the temperature was raised to 335, plus or minus 5 F., and heldat that level for four hours. At the completion of the heating period acopper strip was immersed in the bath for three minutes and was onlylightly tarnished. The temperature of the reaction mixture was thenlowered to 220, plus or minus 5 F., and 0.8 part by weight of phosphorussesquisulfide was slowly added. This temand the desired rate of sulfurinactivation.

1o phosphorized lard oil may vary between approximately 0.1 and 5% byweight of the gear oil blend. The amount of phosphorotrithioite and/orphosphite required to accelerate the reaction will be dependent on theparticular compound chosen, the amount of active sulfur present Ingeneral, amounts between 0.1 and 5% of the total gear oil blend areeffective.

The amount of solvent extract in the blend may vary from 0 to 100% ofthe mineral oil portion, depending upon the desired V.I. and thecompatibility characteristics of the finished blend. In general, amountsfrom 5 to 30% will prevent precipitation and at the same time give anoil with a commercially desirable V.I. The solvent extract used in theblends reported in the foregoing table had the followingcharacteristics:

perature level was maintained for eight hours with con- Gravity1"'ALEL)"L .w. 13.2 tinuons me'chanical agitation of the reaction"mixture: At. Flash"(C.OICl, 'F.) 550 the end of this period a copperstrip immersed in the Fire (C.O.Cl, F.) 6,40 bath at 220 F. for threeminutes gave a pink coating, in- S.U.S. viscosity at 100 F. 34,000dicating that the reaction was completed. The final .prod- S.U.S.viscosityat"150 F. 2,824 not contained 7.85% sulfur and.0.45% phosphorusby" S.U.S. viscosity at 210 F 404 weight. Viscosity index 17 From anexamination of the table, the following con- Pour point F.) +65 clusionscan be drawn: (1) Blend 1 demonstrates that in Total sulfur (percent)2.39 the absence of a phosphite or phosphorotrithioite theNeutralization number (ASTM D974) 2.8 blend still contained corrosivesulfur after being main- Conradson carbon residue 4.2

Table I Blend No. Composition in parts by weight of gear oil NeutralOil, 200 SUS viscosity at 46.7 46.7 46.7.

100 F., 90 V.I. Bright stock, 160-170 SUS viscosity at 212 F.. 90 V.I.Solvent Extract ulf e ur Sulfurized-phosphorized rd Lead naphthen ate(3ll-00Fb):

Triethyl phosphorotrithioite.

Diethyl hydrogen phosphite Tricre=yl phosphite Viscosity:

at 100 F. at 130 F at 210 F. Viscosity Index.. 3 Minute Cu Strip Test:

Upon reaching bath temperature (approx. hour). After 1 hr. at 200 FAfter 2 hr. at 200 F.. After 24 hr. at 200 F After 1 week at 200 F.

clear and bright;

orange--. orange. clear and bright. clear and bright.

Light orange tained for one week at 200 F; (2) blend 2 demonstrates thatthe addition of 2% of triethyl phosphorotrithioite to blend 1 renderedthe sulfur non-corrosive after the blend was maintained at 200 F. fortwo hours; ('3) blend 3 demonstrates that with the addition of only 1%of triethyl phosphorotrithioite the blend was slightly corrosive afterone week; (4) diethyl hydrogen phosphite in the amount of 1.3% waseffective in rendering the blend non-corrosive after one week, as wasalso true of 3.3% of tricresyl phosphite.

As was previously pointed out, the phosphorotrithioites and thephosphites are effective for inactivating corrosive sulfur in theabsence of naphthenate salt. However, naphthenates such as ammonium,sodium, calcium, lead,

Any solvent extract of high aromaticity (above obtained by extraction ofmineral lubricating oil fractions with solvents selective for separatingparaflinic from aromatic hydrocarbons may be used in place of thespecific extract used in preparing the blends given in the materialwhich has been reacted with 5 to 10% by weight of sulfur and then with0.4 to 5% by weight of phosphorous sesquisuliide until the product issubstantially non-corrosive as measured by the copper strip test, from0.1 to 5% of sulfur, about 0.5 to 2% by weight of may be added to theblend to help accelerate the removal dibenzyl disulfide, and a materialfrom the group consisting of oil soluble alkyl, aryl andarylalkyl-phosphites and phosphorotrithioites in an amount of about 0.5to 4% by weight.

2. A lubricant composition consisting essentially of mineral lubricatingoil, from 5 to 20% by weight of lard oil which has been reacted with 5-to 10% by weight of sulfur and then with 0.4 to 5% by weight ofphosphorus sesquisulfide until the product is substantiallynon-corrosive as measured by the copper strip test, from 0.1 to 5% ofsulfur, about 0.5 to 2% by weightof dibenzyl disulfide, and a materialfrom the group consisting of alkyl, aryl and arylalkyl phosphites andphosphorotrithioites in an amount of about 0.5 to 4% by weight.

3. Lubricant composition in accordance with claim 2 containing about 0.1to 5% by weight of lead naphthenate.

4. Lubricant composition in accordance with claim 3 containingsufficient highly aromatic solvent extract from the extraction ofmineral lubricating oil to substantially prevent precipitation. i

5. Lubricant composition in accordance with claim 4 in which thematerial is triethyl phosphorotrithioite.

6. Lubricant composition in accordance with claim 4 in which thematerial is diethyi hydrogen phosphite.

7. Lubricant composition in accordance with claim 4 in which thematerial is tricresyl phosphite.

References Cited in the file of this patent UNITED STATES PATENTS2,160,577 Maag May 30, 1939 2,212,899 Flaxman Aug. 27, 1940 2,382,115Stucker Aug. 14, 1945 2,391,311 Helmore Dec. 18, 1945 2,422,630Musselman June 17, 1947 2,432,095 Frey Dec. 9, 1947 2,560,542 BartlesonJuly 17, 1951 2,580,005 Cyphers Dec. 25, 1951 2,629,721 Sunde Feb. 24,1953 2,764,547 Fields Sept. 25, 1956 FOREIGN PATENTS Canada Ian. 17,1950

2. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF MINERAL LUBRICATINGOIL, FROM 2 TO 20% BY WEIGHT OF LARD OIL WHICH HAS BEEN REACTED WITH 5TO 10% BY WEIGHT OF SULFUR AND THEN WITH 0.4 TO 5% BY WEIGHT OFPHOSPHORUS SESQUISULFIDE UNTIL THE PRODUCT IS SUBSTANTIALLYNON-CORROSIVE AS MEASURED BY THE COPPER STRIP TEST, FROM 0.1 TO 5% OFSULFUR, ABOUT 0.5 TO 2% BY WEIGHT OF DIBENZYL DISULFIDE, AND A METERIALFROM THE GROUP CONSISTING OF ALKYL, ARYL AND ARYLAKYL PHOSPHITES ANDPHOSPHOROTRITHIOITES IN AN AMOUNT OF ABOUT 0.5 TO 4% BY WEIGHT. 3.LUBRICANT COMPOSITION IN ACCORDANCE WITH CLAIM 2 CONTAINING ABOUT 0.1 TO5% BY WEIGHT OF LEAD NAPHTHENATE.